Samhain ( //, //, or //) is a Gaelic harvest festival held on October 31–November 1. It was linked to festivals held around the same time in other Celtic cultures, and was popularised as the "Celtic New Year" beginning in the 18th century.
Samhain marked the end of the harvest, the end of the "lighter half" of the year and beginning of the "darker half". It was traditionally celebrated over the course of several days. It has some elements of a festival of the dead. The Gaels believed that the border between this world and the otherworld became thin on Samhain; because so many animals and plants were dying, it thus allowed the dead to reach back through the veil that separated them from the living. Bonfires played a large part in the festivities. People and their livestock would often walk between two bonfires as a cleansing ritual, and the bones of slaughtered livestock were cast into its flames.